From: Phil Sutter <phil@nwl•cc>
To: David Laight <David.Laight@ACULAB•COM>
Cc: Stephen Hemminger <stephen@networkplumber•org>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated
Date: Fri, 18 Aug 2017 18:52:23 +0200 [thread overview]
Message-ID: <20170818165223.GD16375@orbyte.nwl.cc> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DD005ADE9@AcuExch.aculab.com>
On Fri, Aug 18, 2017 at 04:32:47PM +0000, David Laight wrote:
> From: Phil Sutter
> > Sent: 18 August 2017 11:52
> > On Fri, Aug 18, 2017 at 09:19:16AM +0000, David Laight wrote:
> > > From: Phil Sutter
> > > > Sent: 17 August 2017 18:09
> > > > To: Stephen Hemminger
> > > > Cc: netdev@vger•kernel.org
> > > > Subject: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated
> > > >
> > > > Signed-off-by: Phil Sutter <phil@nwl•cc>
> > > > ---
> > > > ip/ipntable.c | 3 ++-
> > > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/ip/ipntable.c b/ip/ipntable.c
> > > > index 879626ee4f491..7be1f04d33d90 100644
> > > > --- a/ip/ipntable.c
> > > > +++ b/ip/ipntable.c
> > > > @@ -633,7 +633,8 @@ static int ipntable_show(int argc, char **argv)
> > > > } else if (strcmp(*argv, "name") == 0) {
> > > > NEXT_ARG();
> > > >
> > > > - strncpy(filter.name, *argv, sizeof(filter.name));
> > > > + strncpy(filter.name, *argv, sizeof(filter.name) - 1);
> > > > + filter.name[sizeof(filter.name) - 1] = '\0';
> > >
> > > Why not check for overflow instead?
> > > if (filter.name[sizeof(filter.name) - 1])
> > > usage("filer name too long");
> >
> > sizeof(filter.name) is 1024, which is maybe a bit over the top for
> > something a user would input. So I found a better way avoiding all this
> > at once: I made filter.name a const char *, then just assigned *argv to
> > it. This should be safe since rtnl_dump_filter() and therefore
> > print_ntable() callback is called from inside ipntable_show() so *argv
> > is not accessed outside of it's scope.
> >
> > What do you think?
>
> There isn't a scope problem, *argv is program data (written to unusable
> stack space by the kernel during exec.
Ah, thanks for the info!
> If the filter is done in userpace it is ok, but I'd have thought
> it would be passed to kernel later on?
No, it just calls sends RTM_GETNEIGHTBL to kernel and throws away
anything that doesn't match the filter. So filtering happens in
user space exclusively.
Thanks, Phil
next prev parent reply other threads:[~2017-08-18 16:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-17 17:09 [iproute PATCH v2 0/7] Covscan: Fixes for string termination Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated Phil Sutter
2017-08-18 9:19 ` David Laight
2017-08-18 10:52 ` Phil Sutter
2017-08-18 16:32 ` David Laight
2017-08-18 16:52 ` Phil Sutter [this message]
2017-08-17 17:09 ` [iproute PATCH v2 2/7] xfrm_state: Make sure alg_name " Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 3/7] lib/fs: Fix format string in find_fs_mount() Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 4/7] lib/inet_proto: Make sure destination buffers are NULL-terminated Phil Sutter
2017-08-18 16:37 ` Stephen Hemminger
2017-08-18 16:55 ` Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 5/7] lnstat_util: Simplify alloc_and_open() a bit Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 6/7] tc/m_xt: Fix for potential string buffer overflows Phil Sutter
2017-08-17 17:09 ` [iproute PATCH v2 7/7] lib/ll_map: Make sure im->name is NULL-terminated Phil Sutter
2017-08-18 16:33 ` Stephen Hemminger
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